In the printing of multicolor images on printed sheets, care must be taken to ensure that the subimages register accurately with one another. Orientation lengthwise and laterally of the image can be provided by means of conventional peripheral and lateral register devices on sheet-fed presses. However, the skew of the image cannot readily be corrected by these means. Consequently, transfer devices have been developed that permit skewing of the printed sheets as they are conveyed through the press so that the sheets are properly oriented for accurate subimage registration.
A device of this kind is disclosed in DE-OS 3 400 652. The aim of the sheet-fed press disclosed therein is to enable a correcting cylinder to be adjusted at its control side or end relative to its set-value or reference position. Therefore, the axis of the correcting cylinder is skewed as a whole relative to the adjacent cylinders. Placement of the skew adjuster on the control side permits better control and reduces assembly costs.
The disadvantage of the device disclosed in DE-0S 3 400 652 is that the skewing affects the transmission of drive mechanisms. Displacing the cylinder always causes a skewing, and, in the worst case, even a displacement of a gear in the drive train relative to the adjacent gears. This is true whether the cylinder is displaced directly on the transmission side or on the opposite side, although the position in this connection is not known. Thus, although the device improves sheet transfer, it likewise increases problems in the drive train.
DE-C1 37 04 314 discloses an arrangement for adjusting tooth backlash between the drive gears of sheet-conveying rollers and drums of sheet-fed rotary presses wherein eccentric bushings are provided at both ends for the mounting of each drum. The bushings provide parallel displacement of the drums to adjust the backlash during operation. The arrangement does not provide for skewing the drums and skewing cannot be effected without upsetting drive ratios.